[clang] [llvm] [APInt] Consistently use the terms pdep/pext instead of expandBits/compressBits (PR #205112)

[Jay Foad via cfe-commits]

jayfoad wrote:

As an APLer I'm rather fond of the terms "compress" and "expand". We've been using them since at least 1962. But consistency is good, so no objections from me on the patch.

https://github.com/llvm/llvm-project/pull/205112